1992 Volvo 940 I'm Freezing Up!

I have a 92 Volvo 940 with over 200,000 miles. I had to replace the compressor last year (including new o-rings and dryer) but now after about one hour of continuous use I have a freezing up problem. Just under the part where you charge the system sits a cylinder shaped part, possibly the condensor? Anyway, after about 1 hour of use this underneath part gets a coat of ice on it and the unit will not run as a result. The blowing speed in the cabin is affected from blowing real hard cold air to blowing real light, also blowing out cold air.

Any thoughts, maybe some debris got into the system when the compressor was changed out. Replace the accumulator and dryer have been suggested as solutions.

What say you?

Thanks,

Bob